Integral transverse flanges formed on the distal ends of rectangular ducts are well known in the art. These integral transverse flanges typically utilize angular corner connectors and related hardware to join with the opposing distal ends of matching rectangular ducts having similar integral transverse flanges.
Owing to the vital role played by the integral transverse flanges, the structural integrity, strength and sealing ability of the flanges is of significant consideration.
The prior art, particularly Heilman et al. (U.S. Pat. No. 4,466,641) and Fischer et al. (U.S. Pat. No. 4,579,375), the disclosures of which are incorporated herein by reference, disclose duct connecting systems using integral transverse flanges. These arrangements include a first portion extending perpendicularly outwardly from the duct wall and a second portion bent rearwardly from the outer end of the first portion thereby forming opposing channels. The side edges of an arm of a corner connector are adapted to be snapped and crimped into place in these channels for secure assembly. To hold the adjacent duct sections together, the adjacent sections are bolted to each other at their four corner connectors, thereby forming an assembled section of duct.
Apparatus to manufacture the Heilman et al. invention is manufactured and sold by The Lockformer Company of Lisle, Ill. and is referred to in the industry as the TDC (“Transverse Duct Connector”) system. Apparatus to manufacture the Fischer et al. duct is manufactured and sold by Engel Industries, Inc., of St. Louis, Mo. and is referred to in the industry as the TDF (“Transverse Duct Flange”) system. While both systems have provided the industry with a useful duct system, primarily the TDC system, there remains a need in the industry for improvements to the systems as discussed herein.
FIG. 1 illustrates in cross section the roll-formed shape of the end 10 of one duct, and the roll-formed shape of the end 12 of an adjacent duct as disclosed in Heilman et al. The frame includes a first upturned portion 14 extending perpendicularly outwardly from the duct wall 16 and a second portion 18 bent rearwardly into position opposite an end portion of the duct wall. The width of an arm of a corner connector 20 substantially corresponds to the distance between the rearwardly bent portion 18 and the end portion of the duct wall. The side edges of each such arm of a corner connector 20 are adapted to engage the respective surfaces of the rearwardly bent second portion 18 and duct wall end portion whereby the corner connector 20 is held in position relative to the frame by a retainer means defined by the rearwardly bent second portion 18.
The preferred embodiment of the Heilman et al. invention includes a third outwardly facing return portion 22 at the outward edge of the rearwardly bent second portion 18 thereby forming a bead 24. A first channel 26 is formed between the bead 24 and the outwardly extending upturned portion 14, and a second channel 28 is formed in the duct wall opposite the first channel 26. The side edges of an arm of a corner connector 20 are adapted to be snapped into place in these channels 26, 28 for secure assembly of the corner connectors relative to a frame. It has been found, however, that the corner connectors will b displaced during manufacture and transport of the duct. Therefore, the duct flanges must be crimped (not shown in FIG. 1) over the adjacent arms of a corner connector to secure the corner connector in place within a duct flange.
Pursuant to Heilman et al., when assembling one duct with another, the respective frames and associated corner connectors 20 are brought together, and a bolt 30 or other suitable fastener is employed for achieving the desired connection. Prior to completion of this connection, a gasket 32 may be located between the respective frame portions for conventional purposes.
In order to strengthen the resultant duct joint formed by the Heilman et al. invention, each of the arms of a corner connection 20 is provided with an offset ear which may be used for retaining a stiffener means, comprising a strip of spring steel or the like. Each stiffener means is held at its end beneath the offset ear and at its sides between channels 26 and 28. Furthermore, a clip 34 may also be engaged around the adjacent frame portions to provide a smooth exposed joint and to strengthen the joint.
The Fischer et al. duct flange, illustrated at FIG. 2, uses a modification of the Heilman et al. invention and discloses a duct connecting system having an outstanding web portion 36 extending at 90 degrees from the duct wall 38, with an outward-formed tracking ridge 40 spaced inwardly thereof and formed outwardly of the surface of the assembled duct wall 38. At the outer extremity of the web 36 is an outer flange 42 having a turned-under rounded edge 44, formed at an angle slightly in excess of 180 degrees and terminating in a spring margin 46 which extends back toward the web 36 and normally stands inwardly away from the outer flange 42. “Button lock” lances are said to be provided through the rounded-back edge 44 projecting aft. The spacing between the web 36 and the tracking ridge 40, which corresponds to the spacing from the web 36 of the somewhat bulbous rounded portion of the turned-under edge 44, is fixed to accommodate the side edges of an arm of a corner connector. The depth between the spring margin 46 and the outer surface of the duct wall 38 between the ridge 40 and the web 36, is such that the leg portions of a corner connector will snap into position and are said to be held by the spring margins 46 and the lanced projections, trapped by the tracking ridge 40. However, it has also been found that corner connectors will fall out of the Fischer et al. duct flange without crimping. Accordingly, the duct flange of the Fischer et al. duct, in practice, is crimped to hold a corner connector in place.
As with the Heilman et al. invention, the Fischer et al. duct can be readily joined with an adjacent duct end by means of bolts or fasteners. Furthermore, gasket material may also be located between adjacent frames without difficulty to decrease leakage.
In order to increase duct flange strength about the duct joint formed by the Fischer et al. invention, optional reinforcing bars may be utilized between the arms of adjacent corner pieces. Each bar may be snapped in position behind the outwardly formed ridge 40 and the rounded edge 44 of the outer flange 42, and retained by the lanced projections. If desired, and elongated clip can also be positioned around the joint formed by adjacent duct flanges to support the middle portion of the integral flanges. Incorporation of the clip and reinforcing bar with adjacent duct flanges helps to prevent bellowing and leakage caused by pressure exerted by materials flowing within the duct.
FIG. 3 illustrates yet another known integral transverse flange 52. As shown in FIG. 3, the integral transverse duct flange 52 generally comprises a duct having a duct wall 50, defining an inside surface 54 and an outside surface 56. The flange 52 has an inside surface that is continuous with the inside of the duct wall 50 and an outside surface that is continuous with the outside surface of the duct wall 50. The flange 52 includes an upturned portion 58 extending perpendicularly from the duct wall 50.
More specifically, the flange 52 comprises the upturned portion 58 which extends perpendicularly from duct wall 50 and a second rearwardly bent portion 60 extending opposite a portion of duct wall 50. The end of rearwardly bent portion 60 is turned away from duct wall 50 and rounded back toward the upturned portion 58, forming a return portion 62. Return portion 62 is extended to form a L-shaped double wall portion 64 having a first arm 66 arranged adjacent to and in close relation with the inside surface of rearwardly bent portion 60 and a second arm 68 arranged adjacent to and in close relation with the inside surface of upturned portion 58.
Second arm 68 extends toward duct wall 50 a distance substantially less than the length of upturned portion 58. As also shown in FIG. 3, the second arm 68 of L-shaped portion 64 extends a distance less than half the length of upturned portion 58.
Although the integral transverse flanges illustrated in FIGS. 1–3 are suitable for a wide range of applications, there exists a need in the art for structurally stronger integral transverse flanges having an increased sealing capability.
With the forgoing problems and concerns in mind, it is the general object of the present invention to provide integral transverse flanges for a duct connecting system that will evidence a strengthened first upturned portion, a smooth mating surface between opposing transverse flanges and a defined channel to accommodate a sealant or the like.